I agree about not patting the coin dry, mistake in my opinion. But like so many other things it has been repeated so many times that people think it is OK.
This can be especially true with copper coins. Copper seems to almost "attract" a film of oil to itself and you never really see a copper coin without this film. After a dipin acetone a copper coin can have a ghastly dry appearance. If it does that can be corrected witha a VERY light coatin of mineral oil or a silicone based oil such as that found in blue ribbon coin conditioner. The problem is getting the film on thin enough and evenly With as highly volitile as acetone is that isn't really a problem. A few seconds and most of it is gone, a couple minutes and it is GONE. You are much more likely to risk damage from traces of water left on the surface of the coin from a water rinse. I do tend to do a water rinse, but then I do a final acetone rinse to make sure all of the water is gone.
Thanks for the url RLM, quite interesting. I decided to switch to brown/amber glass containers for the rinsing. I have always used such for acetone storage outside of the can.It can't hurt to use them for each step. Jim
